djessence

Hey All,

Am doing a rebuild for my 85 GSL. My housings are shot as are my spare engine housings so i need new ones.

I am able to buy housings through Mazdamotorsports and have some options.

I can Get Stock 12A housings (north american version) or i can get J-spec 12A Rotor housings (which have "the largest of all exhaust ports")

Does having a large exhaust port but not a ported engine help at all?

Will i still be able to use any header made for the 12A?

Any opinions on which i should do?

Thanks in Advance

Edit: I should mention the j-spec housings are $10 cheaper than stock 12A from North America

Vashner

Yea you need a street port at least or the intake's going to be the same CFM flow.

Correct me if wrong I don't know **** about the Jspec just speculating with general physics.

Jeff20B

iTrader: (13)

You can use 12A turbo rotor housings (with their larger than north american ports) with unported intake ports. It works great in an automatic '84 RX-7. I posted a thread about it around a year ago.

sctty

Where are the Japanese rotor housings still available? The last time I heard, Mazda Motorsports didn't have anymore.

djessence

Touche, Scotty, Added to cart and checked availibility and they are on back order......so im going to assume they have none.

Sorry for wasting everyones time lol

Im gonna try and find your thread Jeff cuz im curious now.

djessence

I found your thread Jeff, but it just says that you used them. Is there any advantage or anything (obviously it doesnt matter cuz i cant get ahold of them anymore but im curious)

Jeff20B

iTrader: (13)

They open at the same time as US-spec I believe, but close a few degrees later. That's it. As for any advantages, they are like a mild streetport. If you like how a mild streetport runs and drives, these rotor housings can save you some porting time. Also if you wanted to add a turbo, again some of the work has already been done.

djessence

Does anyone know what the difference is between the rear housing and the front housing (rotor) on the J-spec/12AT engine is?

Was wondering if anyone knew since they are a different part number

Jeff20B

iTrader: (13)

An emissions hole below the exhaust port.

djessence

So if i dont have emissions i could use 2 front housings? Or 2 rear housings? Which one is the emissions hole on

Sorry for all the questions Jeff, but i may be able to get my hands on some so im just trying to get everything figured out

j9fd3s

iTrader: (3)

the jspec housings close 10degrees later, and those engines were rated @110hp, so you're looking at around a 10% increase

the emissions holes on front and rear housings are for the air injection passages, for some reason mazda likes to only drill one on one side. on the us 12a's they drill both sides and this makes the housings interchange front and rearl

if you have no emissions, and dont want to ever, then it doesnt matter, 2 fronts, 2 rears is fine. if you want to be able to run emissions at some point, you can still do 2 fronts or 2 rears, and the emissions hole can be drilled, its very easy, but the engine has to be apart to do it.

if it was mine i would either get the correct housings, or drill the holes, ive seen a few cars (i'm in CA we smog everything) that didnt pass because the housings were swapped, and that really sucks, cause then you need an engine...